A vehicle may coast from time to time and the vehicle may decelerate while coasting due to friction losses and windage losses. A controller of the vehicle may schedule a downshift of a step ratio automatic transmission in response to the vehicle decelerating below a threshold shift schedule vehicle speed. By downshifting the transmission, the vehicle may be prepared to accelerate at a later time. Further, downshifting the transmission may help to keep engine speed within a desired range. However, if the vehicle is decelerating and transmission input shaft torque is lower than desired, a torque disturbance may propagate through the driveline when the transmission downshifts. Therefore, it would be desirable to provide a way of controlling transmission input shaft torque so that driveline torque disturbances may be reduced.
The inventor herein has recognized the above-mentioned issues and has developed a driveline operating method, comprising: adjusting torque of a motor, adjusting a state of an engine cylinder poppet valve actuator, and adjusting a fuel injector operating state via one or more controllers in response to an increase in requested transmission input shaft torque and a transmission downshift request during vehicle coasting.
By adjusting torque of a motor, state of an engine cylinder poppet valve, and state of a fuel injector, it may be possible to reduce the possibility of driveline torque disturbances while a vehicle is coasting and a downshift is requested. For example, driveline torque disturbances may be reduced via increasing a transmission input shaft torque in response to a downshift request while a vehicle is decelerating. The transmission input shaft torque may be increased via entering a deceleration cylinder cut off mode from a deceleration fuel shut off mode. Thus, transmission input shaft torque may be increased without activating cylinders or increasing torque output from a motor of the driveline. In other examples, selected engine cylinders may be activated to increase the transmission input shaft torque in response to the transmission downshift request.
The present description may provide several advantages. In particular, the approach may reduce vehicle driveline torque disturbances. Further, the approach may manage driveline torque in a way that reduces vehicle fuel consumption. Further still, the approach may improve downshifting via coordinated control of a motor and an engine in ways that may be less noticeable to vehicle occupants.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.